My iPhone restarts "randomly" when the battery is below a certain threshold (which I haven't been able to specifically pinpoint). A couple weeks ago I had the battery replaced with a new one, as battery life wasn't longer than just a couple of hours
The device has iOS 10.2.1, to be upgraded to 10.3 hopefully during the day.
Any ideas of what could be wrong? I've read suggestions about resetting the iPhone, but just sound like a pretty rough/brute solution to implement, although it's an alternative indeed.